Nonpolar and Semipolar Nitride Substrate Area Expansion
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Solution Overview
Problem
Current nitride technology faces challenges in producing large area, high quality freestanding nonpolar and semipolar substrates due to limitations in heteroepitaxial growth and polarization effects, which restrict the adoption of nonpolar and semipolar GaN substrates in the III-nitride industry.
Innovation Solution
A method involving multiple slicing and growth steps to geometrically increase the surface area of nonpolar or semipolar substrates by changing the growth direction, including growing III-nitride on a first plane and slicing or polishing along a second plane to achieve nonpolar or semipolar orientations, thereby enlarging the substrate area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heteroepitaxial growth is used to produce nonpolar and semipolar substrates, then device performance is improved by reducing polarization effects, but substrate area remains limited making industrial adoption difficult
Solution Approach 1:
The patent applies dimensionality change by transitioning from growth along the polar c-direction to growth along nonpolar a-direction or semipolar directions. This dimensional change in crystal orientation enables the substrate to expand in lateral area while maintaining high quality, as the nonpolar and semipolar orientations allow for larger feasible substrate diameters compared to conventional c-plane growth
Solution Approach 2:
The patent changes the crystallographic orientation parameter from polar c-plane to nonpolar a-plane or semipolar orientations. This parameter change in growth direction fundamentally alters the polarization characteristics, reducing spontaneous and piezoelectric polarization effects while simultaneously enabling larger substrate areas suitable for industrial production
2Area of stationary object
If c-plane growth is used, then substrate area can be larger, but polarization effects cause quantum-confined Stark effect reducing carrier recombination efficiency
Solution Approach 1:
The patent changes the crystallographic orientation parameter from polar c-plane to nonpolar a-plane or semipolar orientations. This parameter change fundamentally alters the polarization characteristics, reducing spontaneous and piezoelectric polarization effects that cause quantum-confined Stark effect, thereby improving carrier recombination efficiency while maintaining large substrate area
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the production of large area, high quality nonpolar and semipolar nitride substrates, reducing polarization effects and enhancing carrier recombination efficiency, making them suitable for widespread use in III-nitride devices.
Implementation Method 1
These devices are typically grown epitaxially using growth techniques including molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE)
Implementation Method 2
The symmetry elements included in the wurtzite structure dictate that III-nitrides possess a bulk spontaneous polarization along this c-axis, and the wurtzite structure exhibits inherent piezoelectric polarization
Data Source
AI summary
A method for fabricating a high quality freestanding nonpolar and semipolar nitride substrate with increased surface area, comprising stacking multiple films by growing the films one on top of each other with different and non-orthogonal growth directions.